Bare-backed rousette

It was described as a new species in 1980 by Bergmans and Hill. The holotype had been collected in 1977 in northern Sumatra. The species name "spinulatus" is from Latin spina meaning "spine" and ala meaning "wing;" the scientific name refers to the fact that the wings insert along the spine rather than the sides of the body, which is unique in the genus Rousettus.[3]

It is a small megabat with a cone-shaped snout. Its face has a number of small warts on its chin, around its mouth, and between its upper lip and eyes. Its wings are short and broad.[3] Its forearm length is approximately 83–89 mm (3.3–3.5 in). Individuals weigh 88–94 g (3.1–3.3 oz).[4]

It is nocturnal, roosting in sheltered places during the day such as caves. They navigate and potentially locate food resources using a primitive form of echolocation. They create high-pitched buzzing calls by moving the tongue against the palate.[4] Food sources may include nectar and fruit,[1] though it is alleged that they eat edible-nest swiftlet eggs and hatchlings, causing damage to the economically valuable nests.[4]

Its range includes Indonesia and Malaysia. It is found at elevations up to 300 m (980 ft) above sea level.[1]

As of 2008, it is evaluated as a vulnerable species by the IUCN. It meets the criteria for this assessment because its population is estimated to have declined by more than 30% from 1993–2008; this decline is projected to continue.[1]